This invention relates to a method for fabricating semiconductor integrated circuit devices including semiconductor devices, and more particularly, to a technique useful for application to the formation of gate oxide films (insulating films) such as of MOSFET (metal oxide semiconductor field effect transistor).
In the initial stage of semiconductor industries, bubbling was in wide use where a carrier gas such as oxygen or the like was passed through water in a bubbler. Although this technique was advantageous in that a wide range of a moisture content could be covered, a problem on pollution could not be avoided, and thus, the technique is rarely used at present. Accordingly, an oxygen and hydrogen combustion method, i.e. a pyrogenic system, has been widespread in order to avoid the disadvantage of the bubbler.
(Disclosure of Prior Art Literature, etc.)
With regard to an improvement in thermal oxidation and a moisture generation method therefor, to which the invention is directed, the following prior art techniques are known.
(1) In Japanese Patent Laid-open No. Hei 6-163517 of Ohmi, there is described a low temperature oxidation technique of lowering temperatures in a semiconductor process. In Example 1 of this application, there is set out a method wherein hydrogen is added to a gas atmosphere comprising about 99% of argon and about 1% of oxygen in an amount of from 100 ppm to 1%, from which steam is obtained at a hydrogen combustion temperature of 700xc2x0 C. or below, particularly, at 450xc2x0 C. or below, by the action of a stainless steel catalyst. Moreover, in Example 2 of the application, it is stated to thermally oxidize silicon in an atmosphere consisting of 990% of oxygen and 1% of steam formed by use of a catalyst at normal pressures or under pressure at an oxidation temperature of 600xc2x0 C.
(2) Japanese Patent Laid-open No. Hei 7-321102 (Yosikoshi) describes high temperature thermal oxidation on silicon surfaces at an oxidation temperature of 850xc2x0 C. at a very low moisture concentrations i.e. 0.5 ppm of a very super low moisture content region or in a dry region, in order to avoid various problems ascribed to moisture.
(3) In Japanese Patent Laid-open No. Sho 60-107840 of Honma et al, there is described a thermal oxidation method of silicon wherein in order to reduce variations in moisture content caused by moisture in a dry oxidation environment, a very small content of moisture at a level of about several tens of ppm formed according to a conventional method is purposely added.
(4) Japanese Patent Laid-open No. 5-152282 (Ohmi I) discloses a thermal oxidation apparatus which has a hydrogen feed pipe whose inner surfaces are constituted of Ni (nickel) or a Ni-containing material in order to prevent the generation of particles from the tip of a quartz tube as set out hereinabove, and also has means for heating the hydrogen gas feed pipe. In this thermal oxidation apparatus, water is formed by bringing hydrogen into contact with Ni (or the Ni-containing material) inside the hydrogen gas feed pipe heat to 300xc2x0 C. or over, and reacting the hydrogen activated species with oxygen or (an oxygen-containing gas). More particularly, water is formed according to a catalytic system involving no combustion, so that there is no possibility that the hydrogen feed pipe melts at its tip end to cause particles to be generated.
(5) Japanese Patent Laid-open No. Hei 6-115903 (Ohmi II) discloses a moisture generating method using a catalyst system which comprises the mixed gas-preparing step of mixing oxygen, hydrogen and an inert gas to prepare a first mixed gas, and the moisture-generating step wherein the first mixed gas is introduced into a reactor tube constituted of a material, which has the catalytic action and is capable of conversion of hydrogen and oxygen into radicals and the reactor tube is heated to cause the hydrogen and oxygen present in the first mixed gas to be reacted thereby causing water to be generated.
According to this method, a catalytic material, with which the reaction is able to proceed at lower temperatures, is used as the reaction tube for reaction between hydrogen and oxygen. Eventually, generation of water is enabled at low temperatures. Accordingly, where the mixed gas of hydrogen, oxygen and an inert gas is fed to a heated reaction tube, hydrogen and oxygen undergo complete reaction therebetween in the reaction tube at a temperature of 500xc2x0 C. or below. Thus, a gas containing moisture can be obtained at temperatures lower than that of a combustion system.
Moreover, if a metal material alone is used for a gas contact portion after exclusion of all plastic materials therefrom and the metal surfaces are subjected passivation treatment, gases (moisture, hydrocarbons and the like) released from the surfaces become very small in amount. This permits more purified moisture to be generated in higher accuracy in a wide range of concentration (covering ppb to %). The passivation treatment is performed by thermally treating a stainless steel, which has been subjected to electrolytic polishing or electrolytic composite polishing, in an acid or weakly acidic atmosphere with an impurity concentration of several ppb or below.
(6) Japanese Patent Laid-open No. Hei 5-141871 (Ohmi III) discloses a thermal treatment apparatus which includes, as least, an opening capable of opening and closing it, through which an article to be treated is carried out and in, a furnace core tube having a gas supply port through which a gas is supplied thereinto, a heating means for heating the inside of the furnace core tube, a gas supply tube connected in communication with the gas supply port, and heating means for heating the gas supply pipe wherein at least inner surfaces of the gas supply pipe is made of Ni (or a Ni-containing material).
This thermal oxidation apparatus is provided with a hydrogen activated species-generating means for forming hydrogen activated species from a hydrogen gas or hydrogen-containing gas without involving generation of a plasma, which is located upstream of a position of an article to be treated which is placed inside the furnace core tube. A hydrogen gas or hydrogen-containing gas is introduced into the hydrogen activated species-generating means to generate activated species of hydrogen. To this end, if a silicon substrate formed with an oxide film thereon is, for example, placed in the furnace core tube as an article to be treated, the activated species of hydrogen diffuse into the oxide film and contributes to termination of dangling bond in the oxide film and at the interface of the oxide film/silicon. Thus, it can be expected to obtain a gate oxide film of high reliability.
(7) In Japanese Patent Laid-open No. Hei 5-144804 of Nakamura et al, there is set forth a technique of thermal treatment of a silicon oxide film with activated species of hydrogen formed by use of a nickel catalyst.
(8) At pages 128 to 133 of the Lecture Papers at the 45th Symposium of the Semiconductor Integrated Circuit Techniques promoted by the Committee of Electronic Materials of the Association of Electrochemistry, there is reported a silicon oxidation process in a strongly reductive atmosphere mainly comprising hydrogen radicals produced by use of a catalyst for application to a tunnel oxide film of flash memories and hydrogen from moisture.
(9) In Japanese Patent Laid-open No. Hei 6-120206 of Ohmi, there is described a sintering technique using hydrogen activated species which are produced by means of a nickel catalyst for an insulating film insulating and isolating a selective epitaxial growth region therewith.
(10) In Japanese Patent Laid-open No. Sho 59-132136 of Kobayashi et al, there is set out a process of oxidizing and reducing silicon and a refractory metal in an oxidative and reductive mixed atmosphere of moisture and hydrogen generated by an ordinary method.
(Discussion on Prior Art and the Invention)
In the most recent MOS devices, which are fabricated according to a deep submicron design rule, it is required to form a gate oxide film, which is very thin at 10 nm or below, in order to keep electric characteristics of the finely divided elements. For instance, where a gate length is at 0.35 xcexcm, a required thickness of the gate oxide film is at approximately 9 nm. If the gate length is at 0.25 xcexcm, it is assumed that the oxide film thickness becomes so thin as to be at approximately 4 nm.
In general, a thermal oxidation film is formed in a dry oxygen atmosphere. Where a gate oxide film is formed, it has been conventional to use a wet oxidation process (usually at a ratio in partial pressure of moisture of several tens of %) for the reason that the density of defects in the film can be reduced. According to the wet oxidation process, moisture is formed as a result of the combustion of hydrogen in an atmosphere of oxygen, and the moisture is supplied to the surface of a semiconductor wafer (e.g. a wafer for making an integrated circuit or a mere integrated circuit wafer) along with oxygen, thereby forming an oxide film. In view of burning of hydrogen, hydrogen is ignited after oxygen has been sufficiently passed beforehand in order to avoid the danger of explosion. Additionally, the concentration of moisture in a mixed gas of hydrogen+oxygen serving as oxidation species is increased to a level of about 40% (a partial pressure of moisture occupied in a total pressure in the atmosphere).
However, it is indicated that the above combustion system has the problem: since hydrogen is ignited and burnt while being injected from a quartz nozzle attached at the tip of a hydrogen gas supply pipe, the resultant flame comes too near to the nozzle under conditions where the amount of hydrogen is too small; and the nozzle eventually melts by application of heat thereto to cause particles to be generated, which serve as a pollution source of a semiconductor wafer (on the contrary, if the amount of hydrogen is increased in excess, the resultant flame arrives at an end portion of the combustion tube, so that the quartz walls are caused to be melted, thereby generating particles, or the flame is cooled at the wall surfaces and may be put out, thereby presenting a problem on safety). Moreover, in the combustion system, the moisture concentration in the water+oxygen mixed gas serving as oxidation species is so high that hydrogen and a OH group are taken in the gate oxide film. As a result, structural defects such as of an Sixe2x80x94H bond, an Sixe2x80x94OH bond and the like are liable to be produced in the thin film or at the interface with a silicon substrate. These bonds are broken down by application of a voltage stress, such as hot carrier injection, to form a charge trap, thereby causing electric characteristic of the film such as a variation in threshold voltage to be lowered.
It will be noted that the details of these situations and the details in an improved water-forming device using a novel catalyst are described in Japanese Patent Laid-open No. Hei 9-172011 of the present inventors and International Patent Laid-open No. PCT/JP97/00188 (international filing date: Jan. 27, 1997) of the present inventors and Ohimi et al.
According to the studies made by us, known oxidation formation methods are difficult in forming a very thin gate oxide film of a high quality and with a thickness of 5 nm or below (although it is as a matter of fact that similar effects can be expected when the thickness is 5 nm or over) in a uniform thickness and in high fidelity. Needless to say, the formation of a thicker film is also unsatisfactory in many respects.
In order to form a very thin oxide film in a uniform thickness in high fidelity, it is necessary to form a film at an oxide film growing rate lower than that for the formation of a relatively thick oxide film and under more stable oxidation conditions. For instance, in the oxidation film formation method using such a combustion system as set out before, the moisture concentration in a water+oxygen mixed gas serving as oxidation species can be controlled only within a range of concentration as high as from 18% to about 40%. Under these conditions, the oxidation film growth rate is so high that with a thin oxide film, the film can be formed within a very short time. On the other hand, if the oxidation is carried out at a wafer temperature of 800xc2x0 C. or below in order to lower the film growth rate, the film quality lowers (although the present invention is, of course, applicable to in a temperature range of 800xc2x0 C. or below by appropriately controlling other parameters).
For the formation of a clean oxide film, it is necessary to remove a low-quality oxide film formed on the surface of a semiconductor wafer by wet cleaning beforehand. However, a thin natural oxide film is inevitably formed on the wafer surface on the way of transferring the wafer from the wet cleaning step to an oxidation step. Moreover, in the oxidation step, an undesirable initial oxide film is formed on the wafer surface by contact with oxygen in the oxidation species prior to intended oxidation. Especially, with the oxide film formation method using a combustion system, hydrogen is burnt after sufficient flow of oxygen in order to avoid the danger of explosion of hydrogen, so that a time of the wafer surface being exposed to oxygen is prolonged, thereby forming a thick initial oxide film (it is accepted that explosive combustion of hydrogen, i.e. xe2x80x9cexplosionxe2x80x9d, takes place under conditions of normal pressures, a temperature of 560xc2x0 C. or over, a hydrogen content of 4% of over, and a sufficient content of oxygen).
In this way, an actual oxide film has an arrangement that includes, aside from an oxide film formed by intended oxidation, a natural oxide film and an initial oxide film. These natural oxide film and initial oxide film are both lower in quality than the intended, intrinsic oxide film. Accordingly, in order to obtain a high-quality oxide film, it is necessary to suppress the ratio of the lower-quality films to the total oxide film to a level as low as possible. Nevertheless, when a very thin oxide film is formed according to known oxide film formation methods, the ratio of these lower-quality films rather increases.
For example, when a 9 nm thick oxide film is formed using a known oxide film formation method wherein the thicknesses of a natural oxide film and an initial oxide film in the oxide film are assumed to be at 0.7 nm and 0.8 nm, respectively, the thickness of the intrinsic oxide film is at 9xe2x88x92(0.7+0.8)=7.5 nm. The ratio of the intrinsic oxide film in the total oxide film is at about 83.3%. However, when a 4 nm thick oxide film is formed according to the known oxide film formation method, the thicknesses of a natural oxide film and an initial oxide film are not changed at 0.7 nm and 0.8 nm, respectively, the intrinsic oxide film thickness is thus at 4xe2x88x92(0.7+0.8)=2.5 nm, with its ratio being lowered to 62.5%. More particularly, if a very thin film is formed according to the known oxide film formation method, not only uniformity and fidelity of a film thickness are not assured, but also the quality of the film lowers.
In order to solve these problems, we made attention to moisture generation methods of Ohmi et al using catalysts. According to our studies, these methods place emphasis on the strong reduction action of hydrogen radicals on the assumption that xe2x80x9cthe life of hydrogen radicals is longxe2x80x9d. Therefore, it will be apparent that these methods cannot be applied to a mass-production process of semiconductor integrated circuits as they are. In other words, for application to a semiconductor process, we have found that necessary parameters have to be studied on the assumption that xe2x80x9cthe life of hydrogen radicals is very short, and the radicals are generated on a catalyst and are chemically combined or returned to a ground state thereon or in the vicinity of the catalystxe2x80x9d.
Further, according to the present inventors, it has been made clear that a ratio of partial pressure of moisture ranging from 0 to 10 ppm belongs to a dry region wherein a nature of so-called dry oxidation appears, which is inferior to so-called wet oxidation with respect to the film quality required for a gate oxide film and the like in a fine process described hereinafter.
Likewise, we have found that a super low moisture region, wherein a partial pressure ratio of moisture ranges from 10 ppm to 1.0xc3x97103 ppm (i.e. 0.1%), principally exhibit a nature substantially same as dry oxidation.
Moreover, it has also been found that thermal oxidation in a low moisture region covering a moisture partial pressure ratio in the range of form 0.1% to 10% (especially, in a low moisture region covering a moisture partial pressure ration in the range of 0.5% to 5%) is relatively better in properties than those in other regions (including a dry region, a region ordinarily employed in a combustion system of 10% or over, and a high moisture region having a moisture concentration of several tens of % attained by use of a bubbler or the like).
(Objects, etc. of the Invention)
An object of the invention is to provide a technique wherein a high-quality very thin oxide film is formed in a uniform thickness and in high fidelity.
The above and other objects and novel features of the invention will become apparent from the description of the present specification and the accompanied drawings.
Among the inventions disclosed in this application, typical ones are briefly summarized as follows.
A method for fabricating a semiconductor integrated circuit device of the invention comprises the steps (a) and (b).
(a) the step of generating water from hydrogen and oxygen by the catalytic action, and
(b) the step of feeding oxygen containing a low concentration of the water to or in the vicinity of a main surface of a semiconductor wafer heated to a predetermined temperature, under which an oxide film having a thickness of 5 nm or below is formed at an oxide film formation rate sufficient to ensure, at least, fidelity in the formation of an oxide film and uniformity in the oxide film thickness.
In the method for fabricating a semiconductor integrated circuit device of the invention, the oxide film comprises a gate oxide film of MOSFET.
In the method for fabricating a semiconductor integrated circuit device of the invention, the oxide film has a thickness of 3 nm or below.
In the method for fabricating a semiconductor integrated circuit device of the invention, the semiconductor wafer is heated to a temperature of 800xc2x0 C. to 900xc2x0 C.
The method for fabricating a semiconductor integrated circuit device of the invention further comprises, after (b) step, subjecting the primary surface of the semiconductor wafer to oxidizing and nitriding treatments to segregate nitrogen at the interface between the oxide film and the substrate.
In the method for fabricating a semiconductor integrated circuit device of the invention, the oxide film is formed by single wafer processing.
In the method for fabricating a semiconductor integrated circuit device of the invention, the oxide film is formed in a batchwise manner.
A method for fabricating a semiconductor integrated circuit device of the invention comprises the following steps (a) and (b).
(a) The step of forming water from hydrogen and oxygen by the catalytic action, and
(b) the step of feeding oxygen containing the water in a concentration sufficient to provide an initial breakdown voltage, which is better than that of an oxide film formed in am at least moisture-free, dry oxygen atmosphere to or in the vicinity of a main surface of a semiconductor wafer heated to a predetermined temperature to form an oxide film having a thickness of 5 nm or below.
In the method for fabricating a semiconductor integrated circuit device of the invention, the concentration of the water is 40% or below.
In the method for fabricating a semiconductor integrated circuit device of the invention, the concentration of the water ranges from 0.5 to 5%.
The method for fabricating a semiconductor integrated circuit device of the invention comprises the following steps (a) to (c).
(a) The step of transferring a semiconductor wafer having a first oxide film formed on a primary surface thereof to a cleaning unit wherein the first oxide film is removed by wet cleaning,
(b) the step of transferring the semiconductor wafer, without contact with the air, from the cleaning unit to an oxidation unit in an inert gas atmosphere, and
(c) the step of feeding oxygen containing a low concentration of water, which is generated from hydrogen and oxygen by the catalytic action, to or in the vicinity of a main surface of the semiconductor wafer heated to a predetermined temperature, under which a second oxide film having a thickness of 5 nm or below is formed at an oxide film formation rate sufficient to ensure, at least, fidelity in the formation of an oxide film and uniformity in the oxide film thickness.
In the method for fabricating a semiconductor integrated circuit device of the invention, the second oxide film includes a natural oxide film, which is undesirably formed on the surface of the semiconductor wafer during the course between the removal of the first oxide film and the formation of the second oxide film, and an initial oxide film undesirably formed on the surface of the semiconductor wafer by contact with the oxygen wherein the total thickness of the natural oxide film and the initial oxide film is not larger than xc2xd of the whole thickness of the second oxide film.
In the method for fabricating a semiconductor integrated circuit device of the invention, the thickness, in total, of the natural oxide film and the initial oxide film is not larger than ⅓ of the whole thickness of the second oxide film.
A method for fabricating a semiconductor integrated circuit device of the invention comprises the steps of forming a fist oxide film on first and second regions of a semiconductor wafer and removing the first oxide film formed on the first region of the semiconductor wafer, and forming a second oxide film on a first insulating film left in the first region and the second region of the semiconductor wafer wherein at least one of the first and second oxide films is formed according to any one of the methods defined above.
The main features of the invention are described below as numbered.
1. A method for fabricating a semiconductor integrated circuit device, which comprises the steps of:
(a) preparing moisture from oxygen and hydrogen by use of a catalyst at a temperature of 500xc2x0 C. or below; and
(b) forming a silicon oxide film, which serves as a gate insulating film of a field effect transistor, on a surface of silicon by thermal oxidation in an oxidative atmosphere not predominantly comprising hydrogen, in which a ratio of a partial pressure of the prepared moisture to the total atmospheric pressure is in the range of 0.5 to 5%, under conditions where the silicon surface on a wafer is heated to 800xc2x0 C. or over (as is well known in the art, the term xe2x80x9cpredominantlyxe2x80x9d used herein for gas is intended to mean that the intended component in the atmosphere is contained in the largest concentration).
2. A method for fabricating a semiconductor integrated circuit device as recited in 1 above, wherein the oxidative atmosphere contains oxygen gas as its main component.
3. A method for fabricating a semiconductor integrated circuit device as recited in 1 or 2 above, wherein the preparation of the moisture is carried out by acting the catalyst on a mixed gas of oxygen and hydrogen.
4. A method for fabricating a semiconductor integrated circuit device as recited in any one of 1 to 3 above, wherein the thermal oxidation is effected while feeding the oxidative atmosphere to around the wafer.
5. A method for fabricating a semiconductor integrated circuit device, which comprises the steps of:
(a) preparing moisture from oxygen and hydrogen by use of a catalyst at a temperature of 500xc2x0 C. or below; and
(b) forming a silicon oxide film, which serves as a gate insulating film of a field effect transistor, on a surface of silicon by thermal oxidation in an oxidative atmosphere containing oxygen gas, in which a ratio of a partial pressure of the prepared moisture to the total atmospheric pressure is in the range of 0.5 to 5%, under conditions where the silicon surface on a wafer is heated to 800xc2x0 C. or over.
6. A method for fabricating a semiconductor integrated circuit device as recited in 5 above, wherein the thermal oxidation is performed by use of a hot wall furnace.
7. A method for fabricating a semiconductor integrated circuit device as recited in 5 above, wherein the thermal oxidation is performed by use of a lamp heating furnace.
8. A method for fabricating a semiconductor integrated circuit device as recited in any one of 5 to 7 above, wherein a gas containing the prepared moisture is fed as an oxidative atmosphere after dilution with a gas other than moisture.
9. A method for fabricating a semiconductor integrated circuit device as recited in any one of 5 to 8 above, further comprising the step of
(c) subjecting the wafer, on which the oxide film has been formed, to surface treatment in an atmosphere containing nitrogen oxide without exposing the wafer to the air or other oxidative atmosphere.
10. A method for fabricating a semiconductor integrated circuit device, which comprises the steps of:
(a) generating moisture by use of a catalyst at a temperature of 500xc2x0 C. or below; and
(b) forming a silicon oxide film, which serves as a gate insulating film of a field effect transistor, on a surface of silicon by thermal oxidation in an oxidative atmosphere containing oxygen gas, in which a ratio of a partial pressure of the prepared moisture to the total atmospheric pressure is in the range of 0.5 to 5%, under conditions where the silicon surface on a wafer is heated to 800xc2x0 C. or over.
11. A method for fabricating a semiconductor integrated circuit device as recited in 10 above, wherein the oxidative atmosphere contains oxygen gas as its main component.
12. A method for fabricating a semiconductor integrated circuit device as recited in 10 to 11 above, wherein the thermal oxidation is performed while feeding the oxidative atmosphere to around the wafer.
13. A method for fabricating a semiconductor integrated circuit device, which comprises the steps of:
(a) preparing moisture from oxygen and hydrogen by use of a catalyst at a temperature of 500xc2x0 C. or below; and
(b) forming a silicon oxide film, which serves as a gate insulating film of a field effect transistor, on a surface of silicon by thermal oxidation while feeding an oxidative atmosphere containing oxygen gas, in which a ratio of a partial pressure of the prepared moisture to the total atmospheric pressure is in the range of 0.5 to 5%, to around a wafer having the silicon surface heated to 800xc2x0 C. or over.
14. A method for fabricating a semiconductor integrated circuit device as recited in 13 above, wherein the oxidative atmosphere comprises oxygen gas as its main component.
15. A method for fabricating a semiconductor integrated circuit device as recited in 13 or 14 above, wherein the preparation of the moisture is performed by acting the catalyst on a mixed gas of oxygen and hydrogen.
16. A method for fabricating a semiconductor integrated circuit device, which comprises the steps of:
(a) preparing moisture from oxygen and hydrogen by use of a catalyst at a temperature of 500xc2x0 C. or below; and
(b) forming a silicon oxide film, which serves as a gate insulating film of a field effect transistor, on a surface of silicon by thermal oxidation in an oxidation unit while feeding an oxidative atmosphere containing oxygen gas, in which a ratio of a partial pressure of the prepared moisture to the total atmospheric pressure is in the range of 0.5 to 5%, to around a wafer having the silicon surface heated to 800xc2x0 C. or over through a narrowed portion provided between a moisture preparation unit and the oxidation unit.
17. A method for fabricating a semiconductor integrated circuit device as recited in 16 above, wherein the oxidative atmosphere contains oxygen gas as its main component.
18. A method for fabricating a semiconductor integrated circuit device as recited in 16 or 17 above, wherein the preparation of the moisture is performed by acting the catalyst on a mixed gas of oxygen and hydrogen.
19. A method for fabricating a semiconductor integrated circuit device, which comprises the steps of:
(a) preparing moisture from oxygen and hydrogen by use of a catalyst;
(b) diluting a first gas containing the thus prepared moisture with a second gas other than moisture;
(c) introducing the diluted first gas into a treating region; and
(d) forming a silicon oxide film, which serves as a gate insulating film of a field effect transistor, on a silicon surface on a wafer in an atmosphere of the thus introduced first gas in the treating region.
20. A method for fabricating a semiconductor integrated circuit device as recited in 19 above, wherein the oxidative atmosphere contains oxygen gas as its main component.
21. A method for fabricating a semiconductor integrated circuit device as recited in 19 or 20 above, wherein the thermal oxidation is performed at a temperature of 800xc2x0 C. or over.
22. A method for fabricating a semiconductor integrated circuit device as recited in any one of 19 to 21 above, wherein the thermal oxidation is performed while feeding the oxidative atmosphere to around the wafer.
23. A method for fabricating a semiconductor integrated circuit device, which comprises the steps of:
(a) preparing a first gas containing moisture by acting a moisture-preparing catalyst on a mixed gas of oxygen and hydrogen;
(b) diluting the first gas with a second gas other than moisture;
(c) introducing the diluted first gas into a treating region; and
(d) forming a silicon oxide film, which serves as a gate insulating film of a field effect transistor, on a silicon surface on a wafer in an atmosphere of the thus introduced first gas in the treating region.
24. A method for fabricating a semiconductor integrated circuit device as recited in 23 above, wherein the oxidative gas atmosphere contains oxygen gas as its main component.
25. A method for fabricating a semiconductor integrated circuit device as recited in 23 or 24 above, wherein the thermal oxidation is performed at a temperature of 800xc2x0 C. or over.
26. A method for fabricating a semiconductor integrated circuit device as recited in any one of 23 to 25 above, wherein the thermal oxidation is performed while feeding the oxidative gas atmosphere to around the wafer.
27. A method for fabricating a semiconductor integrated circuit device, which comprises the steps of:
(a) preparing a first gas containing moisture by the action of a catalyst;
(b) diluting the first gas with a second gas other than moisture;
(c) introducing the diluted first gas into a treating region; and
(d) forming a silicon oxide film, which serves as a gate insulating film of a field effect transistor, on a silicon surface on a wafer by thermal oxidation in an atmosphere of the thus introduced first gas in the treating region.
28. A method for fabricating a semiconductor integrated circuit device as recited in 27 above, wherein the oxidative gas atmosphere contains oxygen gas as its main component.
29. A method for fabricating a semiconductor integrated circuit device as recited in 27 or 28 above, wherein the thermal oxidation is performed at a temperature of 800xc2x0 C. or over.
30. A method for fabricating a semiconductor integrated circuit device as recited in any one of 27 to 29 above, wherein the thermal oxidation is performed while feeding the oxidative gas atmosphere to around the wafer.
31. A method for fabricating a semiconductor integrated circuit device, which comprises the steps of:
(a) preparing a first gas containing moisture by acting a catalyst on a mixed gas of oxygen and hydrogen;
(b) diluting the first gas with a second gas other than moisture;
(c) introducing the diluted first gas into a treating region; and
(d) forming a silicon oxide film, which serves as a gate insulating film of a field effect transistor, on a silicon surface on a wafer by thermal oxidation in an atmosphere of the thus introduced first gas in the treating region.
32. A method for fabricating a semiconductor integrated circuit device as recited in 31 above, wherein the oxidative gas atmosphere contains oxygen gas as its main component.
33. A method for fabricating a semiconductor integrated circuit device as recited in 31 or 32 above, wherein the thermal oxidation is performed at a temperature of 800xc2x0 C. or over.
34. A method for fabricating a semiconductor integrated circuit device as recited in any one of 31 to 33 above, wherein the thermal oxidation is performed while feeding the oxidative gas atmosphere to around the wafer.
35. A method for fabricating a semiconductor integrated circuit device, which comprises the steps of:
(a) subjecting a silicon surface on a wafer to surface treatment to clean the surface or remove a surface film therefrom;
(b) after the above step, transferring the wafer to an oxidation unit with the wafer being not substantially exposed to an oxidative atmosphere;
(c) preparing moisture from oxygen and hydrogen by use of a catalyst; and
(d) forming a silicon oxide film on the silicon surface by thermal oxidation in an atmosphere containing the prepared moisture.
36. A method for fabricating a semiconductor integrated circuit device as recited in 35 above, wherein the silicon oxide film serves as a gate electrode of an MOS transistor.
37. A method for fabricating a semiconductor integrated circuit device as recited in 36 above, further comprising the step of:
(e) subjecting the wafer having the oxide film formed thereon to surface treatment in an atmosphere containing nitrogen oxide without exposure of the wafer to the air or other oxidative atmosphere.
38. A method for fabricating a semiconductor integrated circuit device as recited in 37 above, further comprising the step of:
(f) forming an electrode material serving as a gate electrode by vapor phase deposition without exposure of the thus surface-treated wafer to the air or other oxidative atmosphere.
39. A method for fabricating a semiconductor integrated circuit device as recited in 36 above, further comprising the step of:
(f) forming an electrode material serving as a gate electrode by vapor phase deposition without exposure of the wafer, on which the oxide film has been formed, to the air or other oxidative atmosphere.
40. A method for fabricating a semiconductor integrated circuit device as recited in any one of 36 to 39 above, wherein the oxidation step is carried out by lamp heating.
41. A method for fabricating a semiconductor integrated circuit device, which comprises the steps of:
(a) subjecting a silicon surface on a wafer to surface treatment to clean the surface or remove a surface film;
(b) after the above step, transferring the wafer to an oxidation unit with the wafer being not substantially exposed the wafer to an oxidative atmosphere;
(c) preparing moisture by use of a catalyst; and
(d) forming a silicon oxide film on the silicon surface by thermal oxidation in an atmosphere containing the prepared moisture.
42. A method for fabricating a semiconductor integrated circuit device as recited in 41 above, wherein the silicon oxide film serves as a gate electrode of an MOS transistor.
43. A method for fabricating a semiconductor integrated circuit device as recited in 42 above, further comprising the step of:
(e) subjecting the wafer having the oxide film formed thereon to surface treatment in an atmosphere containing nitrogen oxide without exposure of the wafer to the air or other oxidative atmosphere.
44. A method for fabricating a semiconductor integrated circuit device as recited in 43 above, further comprising the step of:
(f) forming an electrode material serving as a gate electrode by vapor phase deposition without exposure of the thus surface treated wafer to the air or other oxidative atmosphere.
45. A method for fabricating a semiconductor integrated circuit device as recited in 42 above, further comprising the step of:
(f) forming an electrode material serving as a gate electrode by vapor phase deposition without exposure of the wafer, on which the oxide film has been formed, to the air or other oxidative atmosphere.
46. A method for fabricating a semiconductor integrated circuit device as recited in any one of 41 to 45 above, wherein the oxidation step is performed by lamp heating.
47. A method for fabricating a semiconductor integrated circuit device, which comprises the steps of:
(a) preparing moisture from oxygen and hydrogen by use of a catalyst;
(b) forming a silicon oxide film, which serves as a gate insulating film of a field effect transistor, on a silicon surface on a wafer by thermal oxidation in an atmosphere containing the thus prepared moisture; and
(c) after the above step, subjecting the wafer, on which the silicon oxide film has been formed, to surface treatment in an atmosphere of a gas containing nitrogen oxide without exposing the wafer to the air.
48. A method for fabricating a semiconductor integrated circuit device as recited in 47 above, wherein the silicon oxide film serves as a gate electrode of an MOS transistor.
49. A method for fabricating a semiconductor integrated circuit device as recited in 47 above, further comprising the step of:
(e) subjecting the wafer having the oxide film formed thereon to surface treatment in an atmosphere containing nitrogen oxide without exposure of the wafer to the air or other oxidative atmosphere.
50. A method for fabricating a semiconductor integrated circuit device as recited in 49 above, further comprising the step of:
(f) forming an electrode material serving as a gate electrode by vapor phase deposition without exposure of the thus surface-treated wafer to the air or other oxidative atmosphere.
51. A method for fabricating a semiconductor integrated circuit device as recited in 48 above, further comprising the step of:
(f) forming an electrode material serving as a gate electrode by vapor phase deposition without exposure of the wafer, on which the oxide film has been formed, to the air or other oxidative atmosphere.
52. A method for fabricating a semiconductor integrated circuit device as recited in any one of 47 to 51 above, wherein the oxidation step is performed by lamp heating.
53. A method for fabricating a semiconductor integrated circuit device, which comprises the steps of:
(a) forming an element isolation groove on a silicon surface on a wafer;
(b) forming an insulating film from outside on the element isolation groove;
(c) flattening the silicon surface to expose a portion of the silicon surface on which a thermal oxidation film is to be formed; and
(d) preparing moisture by use of a catalyst and forming a thermal oxidation film serving as a gate insulating film of a field effect transistor on the exposed portion in an atmosphere containing the moisture.
54. A method for fabricating a semiconductor integrated circuit device as recited in 53 above, wherein the flattening is effected according to a chemical mechanical method.
55. A method for fabricating a semiconductor integrated circuit device as recited in 53 or 54 above, wherein the flattening is effected by chemical mechanical polishing.
56. A method for fabricating a semiconductor integrated circuit device as recited in any one of 53 to 55 above, wherein the insulating film from outside is formed by CVD (chemical vapor deposition).
57. A method for fabricating a semiconductor integrated circuit device, which comprises the steps of:
(a) forming element isolation grooves on a silicon surface on a wafer;
(b) forming an insulating film on the element isolation grooves by deposition; and
(c) preparing moisture by use of a catalyst and forming a thermal oxidation film serving as a gate insulating film of a field effect transistor on silicon surfaces surrounded by the element isolation grooves.
58. A method for fabricating a semiconductor integrated circuit device as recited in 57 above, further comprising the step of
(d) flattening the silicon surfaces to expose portions of the silicon surfaces on which a thermal oxidation film is to be formed after the step (b).
59. A method for fabricating a semiconductor integrated circuit device as recited in 57 or 58 above, wherein the flattening is effected by a chemical mechanical method.
60. A method for fabricating a semiconductor integrated circuit device as recited in any one of 57 to 59 above, wherein the flattening is effected by chemical mechanical polishing.
61. A method for fabricating a semiconductor integrated circuit device as recited in any one of 57 to 60 above, wherein the insulating film from outside is formed by CVD (chemical vapor deposition).
62. A method for fabricating a semiconductor integrated circuit device, which comprises the step of heating a silicon surface on a wafer by means of a lamp in an oxidative atmosphere wherein a ratio of partial pressure of moisture to a total atmospheric pressure range from 0.5 to 5%, so that a silicon oxide film, which serves as a gate insulating film of a field effect transistor, is formed on the silicon surface by thermal oxidation.
63. A method for fabricating a semiconductor integrated circuit device as recited in 62 above, wherein the oxidative atmosphere contains oxygen gas as its main component.
64. A method for fabricating a semiconductor integrated circuit device, which comprises the steps of:
(a) forming a first gas containing moisture by acting a catalyst on a mixed gas of oxygen and hydrogen;
(b) diluting the first gas with a second gas;
(c) introducing the thus diluted first gas into a gas treating region; and
(d) forming a silicon oxide film, which serves as a gate insulating film of a field effect transistor, on a silicon surface on a wafer by thermal oxidation in the introduced first gas atmosphere in the treating region.
65. A method for fabricating a semiconductor integrated circuit device, which comprises the steps of:
(a) introducing a non-treated wafer into a oxidation unit which is preheated to a level at which moisture is not condensed and which is kept substantially in a non-oxidative atmosphere; and
(b) forming a silicon oxide film, which serves as a gate insulating film of a field effect transistor, on a silicon surface on the wafer by heating the silicon surface by means of a lamp for thermal oxidation in the oxidation region in an oxidative atmosphere wherein a ratio of partial pressure of moisture to a total atmospheric pressure is in the range of 0.1% of over.
66. A method for fabricating a semiconductor integrated circuit device as recited in 65 above, wherein the non-oxidative atmosphere is mainly comprising nitrogen gas along with a small amount of oxygen gas.
67. A method for fabricating a semiconductor integrated circuit device as recited in 65 or 66 above, wherein the preheating temperature is in the range of from 100xc2x0 C. to 500xc2x0 C.
68. A method for fabricating a semiconductor integrated circuit device as recited in any one of 65 to 67 above, wherein the wafer has a surface temperature of 700xc2x0 C. or over at the time of the oxidation treatment.
69. A method for fabricating a semiconductor integrated circuit device as recited in any one of 65 to 68 above, wherein the non-oxidative atmosphere is preheated to a level at which moisture is not condensed, and subsequently introduced into the oxidation unit.
70. A method for fabricating a semiconductor integrated circuit device as recited in any one of 65 to 69 above, wherein the wafer is preheated to a level at which moisture is not condensed, and subsequently introduced into the oxidation unit.
71. A method for fabricating a semiconductor integrated circuit device, which comprises the step of forming a silicon oxide film, which serves as a gate insulating film of a field effect transition and has a thickness of 5 nm or below, by thermal oxidation in an oxidative atmosphere wherein a ratio of partial pressure of moisture to a total atmospheric pressure range from 0.5 to 5%, under conditions where a silicon surface on a wafer is heated to 800xc2x0 C. or over.
72. A method for fabricating a semiconductor integrated circuit device as recited in 71 above, wherein the oxidative atmosphere contains oxygen gas as its main component.
73. A method for fabricating a semiconductor integrated circuit device as recited in 71 or 72 above, wherein the thermal oxidation is performed while feeding the oxidative atmosphere to around the wafer.
74. A method for fabricating a semiconductor integrated circuit device, which comprises the step of forming a silicon oxide film, which serves as a tunnel insulating film of a flash memory, by thermal oxidation in an oxidative atmosphere wherein a ratio of partial pressure of moisture to a total atmospheric pressure range from 0.5 to 5%.
75. A method for fabricating a semiconductor integrated circuit device as recited in 74 above, wherein the oxidative atmosphere contains oxygen gas as its main component.
76. A method for fabricating a semiconductor integrated circuit device as recited in 74 or 75 above, wherein the thermal oxidation is performed while feeding the oxidative atmosphere to around the wafer.
77. A method for fabricating a semiconductor integrated circuit device, which comprises the steps of:
(a) generating moisture by use of a catalyst;
(b) forming a first thermal oxidation film in a first silicon surface region on a water in a first oxidation unit while feeding an atmospheric gas containing the mixture generated by use of the catalyst to the first oxidation unit;
(c) generating moisture by combustion of oxygen and hydrogen prior to the step (a) or after the step (b); and
(d) forming a second thermal oxidation film in a second silicon surface region while feeding an atmospheric gas containing the moisture generated by the combustion to the first or second oxidation unit.
78. A method for fabricating a semiconductor integrated circuit device, which comprises the step of forming a silicon oxide film, which serves as a gate insulating film of an MOS transistor, on a silicon surface on a main surface of a wafer in an oxidative atmosphere wherein a ratio of partial pressure of moisture to a total atmospheric pressure range from 0.5 to 5%, while keeping the main surface of the wafer substantially horizontal.
79. A method for fabricating a semiconductor integrated circuit device, which comprises the steps of:
(a) preparing moisture, by use of a catalyst, from a mixed gas comprising oxygen in an oxygen-rich amount on comparison with a stoichiometric ratio to water and a non-stoichiometric amount of hydrogen under such temperature conditions that no explosion takes place; and
(b) forming a silicon oxide film on a silicon surface on a wafer by thermal oxidation in an oxidative atmosphere containing the thus prepared moisture.
80. A method for fabricating a semiconductor integrated circuit device, which comprises the steps of:
(a) introducing a wafer to be treated into a high-temperature oxidation unit which is heated to 700xc2x0 C. or over and which is kept in a non-oxidative atmosphere containing a small amount of oxygen sufficient not to substantially cause oxidation to proceed;
(b) preparing moisture from oxygen and hydrogen by use of a catalyst at 500xc2x0 C. or below; and
(c) forming a silicon oxide film, which serves as a gate insulating film of a field effect transistor, on a silicon surface on the wafer by thermal oxidation in the oxidation unit in an oxidative atmosphere wherein a ratio of partial pressure of moisture to a total atmospheric pressure range from 0.5 to 5% under conditions where a silicon surface on the wafer is heated to 700xc2x0 C. or over.
(Other Features, etc. of the Invention)
The above and other features of the invention are summarized below as itemized.
A. A method for fabricating a semiconductor integrated circuit device, characterized by comprising the following steps (a) and (b):
(a) forming water from hydrogen and oxygen by the catalytic action; and
(b) forming an oxide film having a thickness of 5 nm or below on a main surface of a semiconductor wafer at an oxide film growth rate sufficient to ensure, at least, fidelity in the formation of the oxide film and uniformity of the oxide film thickness while feeding oxygen containing the water at a low concentration to the semiconductor wafer heated to a predetermined temperature.
B. A method for fabricating a semiconductor integrated circuit device as recited in A above, characterized in that the oxide film serves as a gate oxide film of MOSFET.
C. A method for fabricating a semiconductor integrated circuit device as recited in A above, characterized in that the oxide film has a thickness of 3 nm or below.
D. A method for fabricating a semiconductor integrated circuit device as recited in A above, characterized in that the heating temperature of the semiconductor wafer is from 800 to 900xc2x0 C.
E. A method for fabricating a semiconductor integrated circuit device as recited in A above, characterized in that after the (b) step, the semiconductor wafer is subjected to oxidizing and nitriding treatment on the main surface thereof to cause nitrogen to be segregated at the interface between the oxide film and a substrate.
F. A method for fabricating a semiconductor integrated circuit device as recited in A above, characterized in that the oxide film is formed by single wafer processing.
G. A method for fabricating a semiconductor integrated circuit device as recited in A above, characterized in that the oxide film is formed in a batchwise manner.
H. A method for fabricating a semiconductor integrated circuit device, characterized by comprising the steps (a) and (b):
(a) forming water from hydrogen and oxygen by the catalytic action; and
(b) forming an oxide film having a thickness of 5 nm or below on a main surface of a semiconductor wafer by feeding oxygen, which contains the water at a concentration sufficient to provide an initial breakdown voltage better than that of an oxide film formed in an at least water-free, dry oxygen atmosphere, to the main surface of the semiconductor wafer heated to a predetermined temperature.
I. A method for fabricating a semiconductor integrated circuit device as recited in H above, characterized in that the concentration of the water is 40% or below.
J. A method for fabricating a semiconductor integrated circuit device as recited in H above, characterized in that the concentration of the water ranges from 0.5 to 5%.
K. A method for fabricating a semiconductor integrated circuit device as recited in H above, characterized in that the oxide film has a thickness of 3 nm or below.
L. A method for fabricating a semiconductor integrated circuit device comprising the steps of (a) to (c):
(a) transferring a semiconductor wafer, which has a first oxide film formed on a main surface thereof, to a cleaning unit wherein the first oxide film is removed by wet cleaning;
(b) transferring the semiconductor wafer from the cleaning unit to an oxidation unit in an inert gas atmosphere without contact of the semiconductor wafer with the air; and
(c) feeding oxygen, which contains a low concentration of water generated from hydrogen and oxygen by the catalytic action, to or in the vicinity of a main surface of the semiconductor wafer heated to a predetermined temperature to form a second oxide film having a thickness of 5 nm or below on the main surface of the semiconductor wafer at a oxide film growth rate sufficient to ensure, at least, fidelity in the formation of an oxide film and uniformity in thickness of the oxide film.
M. A method for fabricating a semiconductor integrated circuit device as recited in L above, characterized in that the oxide film has a thickness of 3 mm or below.
N. A method for fabricating a semiconductor integrated circuit device as recited in H above, characterized in that the second oxide film includes, as part thereof, a natural oxide film undesirably formed on the surface of the semiconductor wafer and an initial oxide film undesirably formed on the surface of the semiconductor wafer through contact with the oxygen during the course of the removal of the first oxide film to the formation of the second oxide film wherein the total thickness of the natural oxide film and the initial oxide film is not larger than xc2xd of the whole thickness of the second oxide film.
O. A method for fabricating a semiconductor integrated circuit device as recited in L above, characterized in that the total thickness of the natural oxide film and the initial oxide film is not larger than ⅓ of the whole thickness of the second oxide film.
P. A method for fabricating a semiconductor integrated circuit device, characterized by comprising the steps of forming a first oxide film on first and second regions of a semiconductor wafer and removing the first oxide film from the first region of the semiconductor wafer, and further forming a second oxide film on the first region of the semiconductor wafer and also on the first insulating film left on the second region wherein at least one of the first and second oxide films is formed by a method comprising the steps (a) and (b) recited in 1 hereinbefore.